The big HOMEMADE TURBO guide

[JDMFantasy2k]

Alright, all i ask is that before you read this that you browse through thermal's "turbo tech files" (click the back button) because there's a lot of good info in there. Especially if you're new to the turbo scene.

First lets cover what a good turbo setup should have:

turbo (duh)
manifold
downpipe
intercooler
charge pipes
oil lines
blow off valve
engine management


Basically, the turbo will add more air into the engine and you need to add the fuel so you don't see your rods all over the road. DETONATION and HORSEPOWER kills motors, not boost. Detonation causes extreme pressures in the motor and sounds like rattling bb's in a coffee can. This can just grenade your motor. When an engine makes more power than it can physically handle, then the motor will break. Usually in hondas the rods let go first (d-series anyway, it seems b-series tend to break ring lands first). As a rule of thumb, a D motor shouldn't run more than 200 whp, and and b-series vary (most LS motors will handle 250-275, and about the same for b18c and b16 but don't hold me to it) Also, realize that 12psi on one turbocharger may be completley different on another. Now an intercooler is not required, but is highly recommended, even for low boost levels. An intercooler can greatly lower intake air temps which will reduce the risk of detonation and make more power.

So lets see how to make a homemade turbo set up.

Manifold

Obviously the exhaust gasses go through this to the turbo. Manifolds vary in shape ( log style, ramhorn, inverted ramhorn, top mount, and other custom designs) and in price (from free to around 800-1000). Now the key to making a Homemade turbo set up is MONEY. Which means if you're going to do it CHEAP then do it good. try not to pay more than 200 for a manifold, and whatever you do DO NOT BUY SSAUTOCHROME. Any and all of the stuff they make (also known as XS POWER) is absolute SHIT, their stuff is that cheap for a reason, it WILL break. Log style manifolds are usually good because of their durability and some can even allow you to retain your AC (don't be a pussy, take it out, it'll be easier). The most cost effective solution for a D series motor is to use a manifold off an old D series motor which had a catalytic converter mounted to the manfold. Then you only need to fabricate an adaptor plate to mate the turbo to the manifold, and you can get the plate and manifold cheap. Another big difference is flow. Obviously a stock honda or log style manifold won't flow as good as a ramhorn will, but price is the limiting factor.


Turbo

Ah the turbo. This will be the largest factor in deciding what power goals you will achieve, and when they will happen. Turbos come in a plethora of sizes and brands. Most turbos are identified as being garrett based, and of using a T3 or T4 frame. Turbos are classified by A/R ratio, trim , and a few other measurements. One factor with turbos is the flanges. Any turbo that is a true T3, will have the same inlet flange, as long as it isn't brand specific. Many car manufactures will equip a T3 turbo on a car and change the inlet flange bolt pattern, in which case you'll need an adaptor plate. Also T4 is a different flange (it's larger) and you can't run a T4 anyway because they're massive. Now a very common T3 tubo that many D series enthusiasts use is the Garrett .48/.60 60 trim. Garrett is the manufacturer ( i think they're the same as airresearch, correct if wrong), but there's also companies like turbonetics, precision, and others, however most of them will follow the T series. Now the .48 is the A/R of the turbine or hot side. .48 is a common size and spools nicely on a d series and is good on a b-series if you have small power goals. The other common size is .63 which is a little laggier, however it will flow more air. A great analogy is picture spraying a pinwheel with a garden hose. If you spray with a nozzle the wheel will spin fast, spray with the open hose, you get a lot of flow. Same thing. A .63 housing is usually a good choice on a b motor cause they are larger displacement (aside from the b16 but it's powerband makes up for that) and will allow better power goals. Turbine wheels also come in trim sizes but for the most part many of them are the same.

The compressor side is much different. Like the turbine side the the housing can be changed out, and is designaged by an A/R ratio (in our example, the housing is a .60). The turbine wheel corresponds with the housing. For example another common turbo to run on a D series is a .48/.42. That turbo will run the exact same exhaust side as the .60, however the compressor side of the .42 will be smaller. Consequently this will also reduce spool time, and the turbo will not flow as much air. Therefore 10 psi out of a .42/.48 is not the same as having 10 psi out of a .60/.48. Compressor wheels also have trim. A common trim size is 60 but there's also 50 and a few others. I'm not exactly sure what the trim measurement is, however i believe it's just an adjustment of the wheel which manipulates airflow.

So what does all this mean? Well if you're boosting a D and you throw on someting like a .63/.60, it'll take longer to spool than a .48/.42, but when the .63/.60 hits full boost it's gonna feel like you fell off a building. The .48/.42 will feel cool too, but won't be as rough. It'll feel more like a little burnout turbo. Spools quick, like to lay tire. So when you chose your turbo, think of your power goals and what you're looking for. Do you want something that spools quick and is awesome in the city, or do you want a laggy 4000 RPM kick in the balls that will make your passengers cry?

Now i've only covered T3's here. Surely there are hundreds of other turbos but i feel T3's are very common turbos and are easy to convert to different spece (which can allow room for growth). A lot of people run mistubishi turbos out of old eclipses and what not. Usually 14B's and variants. Great turbos, but they usually don't flow as much on top. Also if you run one you'll need an adaptor plate. Now be very careful when you buy a turbo. Your best bet is find a nice one from a junkyard if you want to be cheap. Shaft play is the enemy and make sure it doesn't much (in any direction). Otherwise they're pretty simple. If you're going to buy one, ask lots of questions. Make sure you know the size, and ask if it's been rebuilt, if it smokes etc. They have seals and they will blow if they're subjected to high oil pressures or other forms of abuse (compressor surge). Try not to spend more than 200 for a used turbo (pristine). If you spend 250-300 on a remanufactured one you're doing good. Also depends on the size a T3/T4oe is obviously going to cost more than a .42/.48. If you wanna go the junkyard route (no shame in that) then just get something that looks good and start haggling.

Downpipe

This is pretty self explanatory. If you wanted to you could literally run your car open turbo (although it would be stupidly loud, illegal, and make a huge mess). Basically you're gonna need a flange to bolt to the turbo and then just fab the downpipe so it meets up to your exhaust. Luckily T3 flanges are very prominent, and if you look you can find 14B flanges as well. As a rule you don't want a downpipe that is smaller than 2.25 inches. You could make it 2 inch, but don't expect and phenomonial power output. I highly suggest a 2.5 inch downpipe and if you're going to run a good ammount of power then run a 3". Your downpipe will also affect your spool time so don't make it look like a maze. Simple smooth mandrel bends are the best. Check napa for the bends, they have some nice stuff. Also you could pay a local muffler shop to do it for you.

Intercooler

Now the intercooler is optional, but highly recommended. Factory turbo'd cars come with either a top, side or front mount intercooler. The front mount is the most efficient and most common to buy as an aftermarket part. A lot of times you can find cheap front mount intercoolers on ebay for around 200. You can use a used intercooler long as it's in good shape. Hardest part is making sure it fits, so take your bumper off and take some measurements. Lots of people will use DSM sidemount intercoolers and front mount them, some even mount them underhood. This works, but nothing beats having a nice 3x6x30 front mount to cool the boost. Just look around for good stuff and unless you're running a high HP setup which needs some rediculous intercooler, don't spend more than 250. Used dsm sidemounts can be had for 30 bucks so look around.

Charge Pipes

The charge pipes are on the same idea as the down pipe, self explanatory. As a rule of thumb you want the pipe comming out of the turbo to be the same size as the turbo outlet (usually 2") and going into the intercooler. From the there the pipe comming out of the intercooler should be the same as the outlet size and then routed to the throttle body. So most setups will have a 2" pipe out of the turbo then the intercooler and then a 2.5" pipe to the throttle body. Now basically pipe is pipe. Although if you use pvc you can run into problems because i heard it stinks when it heats up and charge temps can reach well over 200*. I used regular stainless steel pipe from advance auto and then i used rubber plumbing couplers from home depot. Although the plumbing couplers work great, they tend to deteriorate after a few months. Eventually you should save for some nice silicone connectors. Ebay piping kits work too, but i think they're too expensive and require just as much work as making your own pipe. Also, rubber elbows make life easy so you only have to work with straight sections of pipe. If you've ever played with Legos, then that skill will come in handy here.